The present invention relates to a controller assembly for use in a vehicle steering system, and more specifically to a controller assembly which is utilized in a hydrostatic steering system having a variable displacement pump which supplies fluid under pressure through the controller assembly to a steering motor.
In copending application Ser. No. 521,236, entitled "Vehicle Steering System", and assigned to the assignee of the present invention, there is disclosed a variety of steering systems which incorporate a metering mechanism which is operable at varying rates in accordance with the steering demanded by the vehicle operator. The systems function to deliver fluid from a source to that metering mechanism in accordance with the rate of operation of the metering mechanism. Advantages of such systems are set forth therein and will not be repeated herein.
The present invention is directed to a controller assembly for use in such systems as disclosed in the aforesaid application Ser. No. 521,236. The controller assembly, in general, includes a directional valve and a metering unit. The controller assembly is connected to the steering wheel so that the valve and metering unit are operated in accordance with the extent and rate of turning of the steering wheel. The controller assembly has a pair of motor ports which are connected with respective opposite chambers of a steering motor, an inlet port connected with a fluid source, preferably a variable displacement pump, and a control port which is connected with a valve assembly, which valve assembly is operable in response to a variation in a pressure signal to effect a change in the displacement of the pump.
To promote the generation of a pressure signal for controlling pump displacement, a variable orifice is provided in the controller assembly. This variable orifice causes the fluid operating pressure conducted to the control port to vary as a function of the rate of rotation of the steering wheel, i.e., the demand for steering. The orifice is formed by cooperation between surfaces disposed on a movable valve member and a housing therefor.
Accordingly, it is an object of this invention to provide a controller assembly for use in a hydrostatic steering system having a variable displacement pump and a pressure-responsive valve and motor arrangement for effecting variations in the displacement of the pump and wherein the controller assembly includes a directional valve, a metering unit and a variable orifice which is effective to cause the fluid operating pressure conducted from a housing control port to vary as a function of variations in steering wheel movement and/or steering loads.